Hello Rohan,
your sine wave is being digitzed at the controller rate of input for that signal. In this case, I'm assuming it's the blue signal. To get higher resolution, you will need to increase the rate of the speed control loop. This will also require you to retune the speed control PI loop. However, your sine wave will always be digitized, and it doesn't matter for testing the speed control loop if it is digitized or not. It might not look like a smooth sine wave, but that doesn't affect anything regarding safety critical opertaion. However, if you have an application that requires higher resolutin of your speed, or smoother transitions between speeds, then that would be a good reason to try and run the speed loop faster and retune the control loop.
